Digital cameras have become small and inexpensive, and as a result, many electronic devices can include a digital camera. Examples of such electronic devices include many portable wireless electronic devices, such as cellular telephones, smart phones, tablet computers, laptop computers, and the like. These cameras can be convenient additions to electronic devices because they are often portable enough to be carried with the user at most times. The camera in a portable device can be used for taking pictures and videos, to document events and communicate with others. The camera can also be used as a data entry or data capture device, where the camera can be configured to scan documents and various types of bar codes. As computer processing power and storage capacity in portable electronic devices increases with improved technology, cameras can be used to capture vast amounts of image data (e.g., still photos and moving video images) and process, store, and communicate such data for many useful purposes.
A digital camera includes a lens that focuses light on a light sensor or image sensor, where the light is reflected from the subject of the scene, and from other objects in the scene. The sensor can convert the light, at each pixel location on the sensor, into digital data.
In many embodiments, before the camera captures image data, a camera sensor can be used to determine a proper exposure value, and whether or not additional illumination would improve the exposure of the scene. To determine a proper exposure value, light from the scene can be allowed into the camera and measured by the camera's image sensor, or by an alternate sensor used for metering a photographic scene. Based on these measurements, calculations can determine an opening size for the camera aperture and a duration for the exposure of the camera sensor.
If the camera determines that the amount of light entering the camera falls below a “low light” threshold, the camera can use an illuminator, or flash, to cast additional light on the scene, and take additional measurements while the illuminator is active. In some embodiments, the illuminator can be implemented with a light emitting diode (LED) that emits a balanced white light. In other embodiments, the illuminator can be implemented with a small incandescent bulb, or with a xenon tube flash. By controlling the illuminator during the metering process, proper values for aperture setting and exposure duration can be calculated before the actual pictures taken.
Disadvantages of using the illuminator to “preflash” the photo include annoying or distracting persons in the photographic scene, using additional time before the photograph is taken, and using energy for the preflash illumination. Persons in the photographic scene can be annoyed by additional flashes of light in the eyes. If too much time is taken before the photograph, a particularly interesting photographic moment may be lost because the camera was not fast enough to capture the image. And with regard to power consumption, conserving battery charge in a battery-powered device is always important to the goal of extending battery life.
In view of these deficiencies in the operation of cameras in electronic devices, an improved apparatus and method for controlling a camera in an electronic device is needed. It is in view of this background information related to the design and use of a camera in an electronic device that the significant improvements of the present disclosure have evolved.